This invention relates to the assembly of headed trim panel fasteners to a composite trim panel.
Motor vehicles today are conventionally trimmed on the inside with composite trim panels of the type having a heavy cardboard or plastic backing layer, an outer ornamental layer of vinyl, cloth, leather or the like, and an intermediate layer of padding or other resilient material. It is desirable to assemble headed fasteners to the backing layer of the trim panel prior to press fitting the fasteners into holes in the body sheet metal to retain the entire trim assembly to the vehicle. Such fasteners in general have a head, a neck of reduced diameter and an elongated shank which includes resilient fins or other elements designed to retain the fastener in the sheet metal hole. It is necessary to mount the head of the fastener between the backing and decorative layers through a hole or slot which has a diameter or width smaller than the head to prevent withdrawal of the head.
One known assembly uses a keyhole shaped slot which consists of two slots opening to one another across a constricted portion. The first slot has a diameter or width larger than the head of the fastener, the second slot has a diameter or width less than that of the head but larger than that of the neck while the constricted portion has a width slightly less than the diameter of the neck. The head of the fastener is received through the first slot and the neck is snapped past the constricted portion into the second slot where it is retained. Such a structure is shown in Fernberg U.S. Pat. No. 3,213,506. This assembly requires that the material of the backing panel have a fairly high resiliency due to the snapping of the neck of the fastener through the constricted portion of the slot. Another known assembly uses a T-shaped slot which consists of two elongated slots opening to one another in a general T-shape and having a width less than the diameter of the head of the fastener such as shown in Fordyce U.S. Pat. No. 3,037,596. The fastener is tilted and the head is slid through one slot as the neck slides through the other slot. This assembly requires tilting of the fastener and is therefore not well suited to being automated. Another known assembly uses a fastener with a head having a general pie-shaped cutout therein. An edge portion of the head is inserted in a slot with a width less than the larger dimension of the head and the fastener is then rotated until the head screws into the slot.